Postoperative Serum Parathyroid Hormone Levels as a Predictor of Hypocalcemia in Patients Undergoing Total Thyroidectomy

Postoperative hypocalcemia is a common complication of total thyroidectomy; the onset and severity of post-operative hypocalcemia is unpredictable. Various attempts have been made to identify predictors of hypocalcemia. There has been an increasing interest in serum levels of parathyroid hormone (PTH) as an early predictor of the development of hypocalcemia after total thyroidectomy. However, there is no consensus on the time intervals and cut-off levels of serum PTH to predict hypocalcemia. In this study, we intend to use serum PTH levels at 4th and 12th hour after total thyroidectomy to identify patients at risk of developing Postoperative hypocalcemia and to evaluate the role of PTH in predicting hypocalcemia. A Cross sectional analytical study conducted in 33 patients undergoing total/completion thyroidectomy from December 2018 to May 2020. Serum total calcium, Serum ionized calcium and Serum intact PTH levels were measured on three occasions (Preoperative and 4th and 12th hour Postoperative). Between both Postoperative levels of PTH, the one with better predictability of hypocalcemia was determined. Postoperative 4th hour PTH is a better predictor of transient hypocalcemia than Postoperative 12th hour PTH, as the association of the former with serum ionized calcium level was statistically highly significant with p value 0.005 and 0.021 respectively. Serum PTH determination after four hours of total thyroidectomy is a relatively better predictor of transient hypocalcemia, and can guide calcium supplementation for those at high risk in the Postoperative period. However, to determine the risk of hypocalcemia at the end of 1 month of follow-up, both the Postoperative 4th and post-operative 12th hour PTH have similar diagnostic accuracy.